Geoff held the record from 2004 to 2006, and has attempted to regain it on several occasions since then. Any attempt on the record requires a day with no track closures and near-perfect running of the network.

"It didn't go entirely smoothly," admits Geoff. "The Piccadilly was suspended for an hour whilst there was a fire at Russell Square, but it may have been that we benefited slightly from the backed up trains running more frequently by the time we got there. It was very smooth, though. Only on one other occasion in the last three years was there a smooth day where the tube didn't break. Something goes wrong on the network almost every day. I love the tube — really, love — but bless it, it's old and breaks a lot."

Challengers can take any route they like and can use scheduled transport (such as buses and overland trains) to move between lines, but any attempt also requires a certain amount of jogging.

"I've been getting fit by running," says Geoff. "You have to be fit to do it, so I knew that a faster time was possible. People have also been goading me saying that 'I'd never beat it', so it was to prove a point to them as well!"

Like most tube challengers, Geoff is coy over the exact route the team took, not wanting to reveal strategies to rivals. All we know is that he finished at Heathrow Terminal 5. Photographic, time-stamped evidence of every station must be sent to Guinness for the time to be confirmed, however.

The obvious question on many people's lips would be 'why?'. What makes someone train for such a bizarre accomplishment?

"A lot of people watch TV and go down the pub week after week and waste their life away. We're well aware that whilst this may be seen as an insanely geeky thing to do, we've also had a lot of fun, friendly times doing it — and best of all, a Guinness World Record certificate."

So what's next for Geoff and the team? Do they have their eyes on other transport records?

"Not really. New York is the only other subway system that Guinness World Records recognises. I think [the London record] will be EXTREMELY HARD to beat now, as we didn't have a lot of slack in our day — so, to be honest, I think what will happen next is that in three years time when the Metropolitan Line is extended to Watford via the Croxley Link, there will be a day where the map — and thus the record — is 'reset' and loads of people will be out on the first day of the new service, trying to set a new time. And I guess i'll be there..."